A relatively new specification for Universal Serial Bus (USB) compliant devices is the Universal Serial Bus Power Delivery Specification, Rev. 2.0, V1.0, published in August 2014, hereinafter referred to as the USB-PD specification. The USB-PD specification describes ways for USB devices to deliver power over a USB cable and through USB ports at a “provider” or source to a “consumer” or sink. The provider may be a USB host and the consumer may be a USB device. In some examples, approximately 5 volts (V) of power may be provided by power sources located at or coupled with a USB host to provide power to a USB device. In other examples, higher voltage levels of approximately 12V or 20V may be provided to the USB device.
The USB-PD specification also describes a scenario where a consumer may at least temporarily switch roles and may provide operating power to the provider. This scenario is called a dead battery condition. In some examples, a USB-PD provider controller at the provider may control a switch to allow power to be routed from the consumer to provide operating power to circuitry at the provider. For these examples, if the provider does not have power then the USB-PD provider controller may use 5V of power from a power source at the consumer to power up and negotiate with a USB-PD consumer controller at the consumer. Negotiations may include timing for closing the switch to enable the 5V voltage level to be routed to the circuitry at the provider.